Multiple problems installing TeX Live 2021 on Windows 10 - windows

Question

I have a Windows 10 laptop where no TeX distribution was ever installed before (double-checked for config directories, files, and environment variables).
Wanting to install TeX Live 2021, I followed the full installation guide and also read the Windows-specific warnings. I've now tried several times, following different installation procedures - cleaning up everything (deleting base & user directories, environment variables, etc) before each time - but still don't manage to get a working installation. Before I report a bug at tex-live#tug, I wanted to ask for advice here, in case I'm doing something wrong. Here is what I did, step by step, and the problems I encountered in the process.
1. First I tried running the recommended online installer install-tl-windows.exe. It never got past the screen that tries to contact or load from a repository, even after a 30-min wait. Tried a dozen times, choosing different mirrors nearby and far away. No luck.
2. Then I downloaded and unpacked the install-tl.zip and run install-tl-windows.bat therein. This time the main installation window appeared. I left all default paths and environment variables (note that I do have write access to C:); in the selection scheme I unselected all languages except US & UK English, unselected XeTeX, LuaTeX, ConTeXt; also unselected TeXworks (I use Emacs), and clicked Install. After one to three hours (depending on the mirror I chose), the installation was complete.
I tried compiling a minimal latex document (see below), and got an error similar to the one in this old question:
I can't find the format file `pdflatex.fmt'
Following the advice in the answers to that question and similar questions elsewhere online such as this, I tried running texhash and fmtutil-sys --all. The latter gave the error
no appropriate script or programme found fmtutil.
for which there are also many posts online.
2a. Not understanding what the problem could be, I re-tried with all possible combinations of the following three options: (a) choosing different mirrors; (b) leaving the full selection of packages (ie without unselecting some languages, LuaTeX etc); (c) redoing the procedure by choosing "Run as Administrator". No luck.
3. At this point I tried downloading the ISO file with the full installation. Mounted the image and run install-tl-windows.bat (as normal user, as recommended; I repeat that I do have write access to C:). Everything proceeded as in step 2. above. At the end of the installation I tried running pdflatex on the minimal latex document. New error this time:
This is pdfTeX, Version 3.141592653-2.6-1.40.22 (TeX Live 2021/W32TeX) (preloaded format=pdflatex)
restricted \write18 enabled.
entering extended mode
(./minimal-template.tex
LaTeX2e <2020-10-01> patch level 4
L3 programming layer <2021-02-18>
! LaTeX Error: File `article.cls' not found.
Very strange. A file search revealed that article.cls is in the TeXLive file system; but kpathsea did not see it indeed.
4. At this point I opened the TeX Live Shell from the Start Menu; selected a CTAN mirror; updated the TL Manager which was not up to date; updated all packages; run Regenerate filename database; and run Regenerate formats. With the latter I got this error:
tex live shell:
mtutil [INFO]: total formats: 59
fmtutil [INFO]: exiting with status 53
C:\texlive\2021\bin\win32\runscript.tlu:915: command failed with exit code 53:
perl.exe c:\texlive\2021\texmf-dist\scripts\texlive\fmtutil.pl --sys --all
Here is a snip from the full set of errors appearing in the "Other" tab (I'm replacing my user directory with asterisks for privacy; note that I do have write access to these directories):
start load https://www.nic.funet.fi/pub/TeX/CTAN/systems/texlive/tlnet
finish load https://www.nic.funet.fi/pub/TeX/CTAN/systems/texlive/tlnet
start load http://contrib.texlive.info/current
finish load http://contrib.texlive.info/current
running mktexlsr ...
done running mktexlsr.
running mtxrun --generate ...
done running mtxrun --generate.
running updmap-sys ...
done running updmap-sys.
regenerating fmtutil.cnf in C:/texlive/2021/texmf-dist
running fmtutil-sys --byengine luatex --no-error-if-no-format --no-error-if-no-engine=luajithbtex,luajittex,mfluajit --status-file=C:\Users\***\AppData\Local\Temp\rPSb0Dpak2\WW_dJvUHgX ...
tlmgr.pl: fmtutil-sys --byengine luatex --no-error-if-no-format --no-error-if-no-engine=luajithbtex,luajittex,mfluajit --status-file=C:\Users\***\AppData\Local\Temp\rPSb0Dpak2\WW_dJvUHgX failed (status 255), output:
Unknown option: status-file
Try "fmtutil --help" for more information.
C:\texlive\2021\bin\win32\runscript.tlu:915: command failed with exit code 255:
perl.exe c:\texlive\2021\texmf-dist\scripts\texlive\fmtutil.pl --sys --byengine luatex --no-error-if-no-format --no-error-if-no-engine=luajithbtex,luajittex,mfluajit --status-file=C:\Users\***\AppData\Local\Temp\rPSb0Dpak2\WW_dJvUHgX
running fmtutil-sys --byengine luajithbtex --no-error-if-no-format --no-error-if-no-engine=luajithbtex,luajittex,mfluajit --status-file=C:\Users\***\AppData\Local\Temp\rPSb0Dpak2\WW_dJvUHgX ...
I tried to continue anyway with Regenerate fontmaps, and then tried again pdflatex on the minimal document. New error:
This is pdfTeX, Version 3.141592653-2.6-1.40.23 (TeX Live 2021/W32TeX) (preloaded format=pdflatex)
restricted \write18 enabled.
---! c:/texlive/2021/texmf-var/web2c/pdftex/pdflatex.fmt made by different executable version
(Fatal format file error; I'm stymied)
5. I tried again steps 3. and 4., but with "Run as Administrator". Same errors.
OK at this point I give up and really don't know what to do. Am I doing something wrong? For the moment I have to concur with this post: installation of TeX Live 2021 is an utter failure.
Here is the minimal latex file I used for testing (copy & paste):
\documentclass{article}
\begin{document}
test
\section{Section}
test
\end{document}

Answer 1

Found, that the download is not working because the system path to "cmd.exe" is not found. Therefore: open a cmd window and add the system path prior to starting the .bat file (set PATH=%PATH%;C:\Windows\system32)